The invention relates to a Jacquard machine, comprising 2 sets of knifes moving up and down in opposition, which each, at their extremities, are taken up in separate knife grids being driven by a cinematic drive chain, and each, at one of their extremities, being guided into a straight motion by means of a “Watt's linkage” rod system, the height of lift of each of these extremities of the knife grids being adjustable, and the knife grids each at their first extremities being linked with at least one first driving lever by means of a first linking rod, and at their second extremities being linked with at least a second driving lever by means of a second linking rod.
The construction of Jacquard machines is subjected to an ever increasing pressure to produce machine at lower prices and operating faster, that are sufficiently strong to realize the forming of the shed required, in an accurate and reliable manner, in order to produce a fabric of the quality required. It is therefore important for the construction of Jacquard machines to build knife drives, driving two sets of knifes moving up and down in opposition, at a minimal prime cost and sufficiently strong. The two sets of knifes moving up and down in opposition on either side of the Jacquard machine are each taken up by a knife grid, such that both at the left and at the right (seen from the position of the weaver looking in the direction from where the warp yarns are supplied) there are two knife grids moving up and down in opposition in the direction of the Jacquard. When the knifes are installed in the warp direction, the terms left and right have to be interpreted as front and back, seen from the position of the weaver looking in the direction from where the warp yarns are supplied.
For a strongly operating machine it is important that the knife grids are moving in a practical vertical position, in order to cause only little vibrations, especially at high operational speeds, in order to obtain a well formed shed as well as to limit the wear and tear of the various components and to increase the machine's endurance. If, at the same time, it will be possible to obtain a reduction of the inertia of the mechanism, vibrations and wear and tear will be further reduced and the endurance will be increased.
For the building of Jacquard machines, solutions are known according to the state-of-the-art, to vertically guide the motion of the knife grids.
So it is known from EP 136 244 to guide both knife grids, practically in their central position by means of a linear guide in order to obtain a vertical motion. Both knife grids are moving one above the other and in opposition, such that it will be possible to make the two grids operate on one linear guide. Such guides, however, are strongly subject to wear. Moreover, the knife grids situated one above the other will cause the height required to install them to be great.
In EP 409 139 the knife grids are guided in their vertical motion at one extremity by a little carriage, attached by a hinge to the extremity of a knife grid, and which has been provided with rollers moving up and down in a vertical guiding slot during the up and down motion of the knife grids, such that this extremity of the knife grid performs a practically vertical motion. The other extremity of the knife grid is moving vertically up and down in a guiding slot, whereas the extremity is free to move in the direction from back to front, seen from the position of the weaver. So, this said other extremity of the knife grid is not moving only vertically, but is free to move in the warp direction of the weaving machine situated below. This way of installing is already more compact as to height than is the case in the one shown in EP 136 244, but also here, the guiding components will cause wear, thus increasing the cost for maintenance and it is no guarantee for a permanent good performance of the Jacquard machine.
In EP 488 915 the knife grids are moving in a frame that is provided with guiding slots, in which the knife grids are moving up and down. The guiding slots are a disadvantage, because there is quite some significant material contact, causing friction and developing heat and the components will be subject to wear. At high speeds, these effects are very disadvantageously increased.
In EP 0 754 791 a “Panhard Rod Guide” is used for each knife grid. With this, the knife grid is guided in its vertical motion by a rod, one of its extremities is hingedly linked up, practically in the centre of the knife grid, and, at the other extremity, is swivelling about a fixed point on the frame of the machine. Because of which the motion of this hinge point between rod and knife grid is reduced to an arch of a circle. When the rod is in a practically horizontal position, a motion following the arc is corresponding to a practically vertical motion through a limited angular displacement. However, the longer the motion of the knife grid, the greater the deviation with respect to the vertical motion. However, the longer the rod, the smaller the deviation, but the more expensive the part and the greater the inertia. For larger Jacquard machines, additional slots are provided at the left and right, having the known disadvantages as far as wear and maintenance costs are concerned.
According to the state-of-the-art, other Jacquard machines are known by the type name of BONAS MJ, a so-called “Watt's linkage” being used to vertically guide the motion of the knife grids. A “Watt's linkage” is a system of rods with three rods, the two outermost rods having the same length, i.e. a first and a second rod, at one of their extremities, hinging about fixed points, which points are not coinciding, and their other extremities, each being linked with one of the extremities of a third rod. This rod system has the property that the centre between the two linking points with the first and the second rod respectively is following a substantially linear motion on this third rod, when the first two rods are rotating about their fixed hinge points. A characteristic of this solution is that it is more wear-resistant and stronger than the said solutions.
In the Jacquard machine of the BONAS MJ type, this principle is applied by adding three rods, constituting the Watt's linkage as described before, to the mechanism in such a manner that the linear motion of the centre of the third rod will be moving vertically. The centre of this third rod is linked with the linking point of a knife grid. In such a Jacquard machine, a substantially vertical motion is imposed on the linking point of the central rod with the knife grid without any appreciable wear being caused and heat being developed. Because of this, wear remains within bounds. However, 3 additional rods and 5 additional linking points with bearings are added per knife grid, considerably increasing both the inertia and the price of the Jacquard machine.